Apparatus for the automatic concentration control of aqueous caustic soda solution

ABSTRACT

An apparatus for the automatic concentration control of an aqueous caustic soda solution in a cloth treating tank through which a cloth to be treated is continuously transported, comprising the provision of a means for adding a neutralization agent to a sample of the caustic soda solution which was squeezed out of a cloth that had been soaked with an aqueous caustic soda solution while in a cloth treating tank; a sensor for detecting the neutralization point of said caustic soda sample solution, to which the neutralization agent is added on the basis of electrical conductivity; a means for detecting the caustic soda concentration of said caustic soda sample solution prior to the addition of the neutralization agent on the basis of the amount of the neutralization agent added until said caustic soda sample solution becomes neutralized as detected by means of said sensor; and a means for supplying a supplementary caustic soda solution to the caustic soda solution in said cloth treating tank so that its concentration is controlled to a prescribed value on the basis of the caustic soda concentration of the caustic soda sample solution detected by said detection means.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for the automaticconcentration control of an aqueous caustic soda solution which is usedin the continuous treatment of a long cloth.

2. Description of the Prior Art

In subjecting a long, commercially produced cloth to such treatments aspretreatment, weight reduction and mercerization continuously, it iscommon to soak the cloth to be treated with an aqueous caustic sodasolution having a prescribed concentration in a cloth treating tank andthen to subject the resultant cloth to treatments such as, heat andtension treatments. In such a treatment with the use of a caustic sodasolution, however, a drawback exists such that the quality of thetreated product becomes uneven due to the fact that the concentration ofthe caustic soda solution changes frequently during the course oftreatment.

Therefore, it is necessary in such a continuous treatment of a cloth, toapply a caustic soda solution having a definite concentration. However,in transporting a long cloth continuously through a cloth treating tankcontaining a treating solution, the concentration of the caustic sodasolution unavoidably becomes lower with time. Conventionally, therefore,the caustic soda concentration in the treating solution tank isdetermined manually at prescribed time intervals, and a supplementarycaustic soda solution is supplied into the cloth treating tank based onthe result of the determination of the controlled concentration of thecaustic soda solution in the cloth treating tank. However, with such amanual operation, problems arise; one being that a skilled operator isneeded and another being that a long time is necessary until thesolution control is completed thus deteriorating the operationefficiency.

SUMMARY OF THE INVENTION

Under such circumstances, the object of the present invention is tooffer an apparatus for the automatic concentration control of an aqueouscaustic soda solution in a process for soaking a long cloth continuouslywith a caustic soda solution in a cloth treating tank.

The essential points of the present apparatus comprises a means foradding a neutralization agent to a sample of the caustic soda solutionsqueezed out of a cloth having been soaked with an aqueous caustic sodasolution in a cloth treating tank; a sensor for detecting theneutralization point of said caustic soda sample solution, to which theneutralization agent is added, on the basis of electrical conductivity;a means for detecting the caustic soda concentration of said causticsoda sample solution prior to the addition of the neutralization agenton the basis of the amount of the neutralization agent added until saidcaustic soda sample solution becomes neutralized, as detected by meansof said sensor; and a means for supplying a supplementary caustic sodasolution to the caustic soda solution in said cloth treating tank sothat its concentration is controlled to a prescribed value on the basisof the caustic soda concentration of the caustic soda sample solutiondetected by said detection means.

BRIEF EXPLANATION OF THE DRAWING

The drawing is an explanatory drawing showing an example of the presentapparatus for the automatic concentration control of an aqueous causticsoda solution.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described in detail in the following withreference to the drawing showing an example of the apparatus.

In the drawing, 1 is a cloth treating tank containing an aqueous causticsoda solution 3, to be applied to a cloth 2 which is transportedcontinuously therethrough, and guide rollers 4 are provided in thissolution tank 1 for immersing the cloth 2 into the solution. 5 is a pairof squeeze rollers for squeezing the excess of caustic soda solution outfrom the cloth 2 after being taken out of the solution tank 1. It isdesigned such that a portion of the aqueous caustic soda solutionsqueezed out from the cloth by means of the squeeze rollers 5 is sent toa sample solution collection container 7 by means of a pump 6, and theother portion thereof is returned to the cloth treating tank 1. 8 is asample solution stirring container into which the caustic soda solutionin the sample solution collection container 7 is transported, by meansof a quantitative pulse pump 9. 10 is a dilution water tank, and 11 isneutralization agent solution tank in which for example, a sulfuric acidsolution is introduced. It is designed such that the dilution water inthe water tank 10 and the neutralization agent solution in theneutralization solution tank 11 are supplied quantitatively into thesample solution stirring container, 8 respectively, by means ofquantitative pulse pumps 12 and 13. 14 is a concentration sensorimmersed in the solution in said sample solution stirring container 8.The characteristic property of the electrical conductivity being loweredextremely at the neutralization point is utilized for the concentrationsensor 14.

15 represents a solution concentration control unit comprising; presetcounters 16 and 17 for detecting the amounts of the caustic sodasolution and the neutralization agent solution supplied into the samplesolution stirring container 8 by means of the quantitative pulse pumps 9and 13, an electrical conductivity measurement circuit 18 by which thepoint at which the electrical conductivity in the concentration sensor14 reaches its minimum is detected, an operation circuit 19 by which thecaustic soda concentration of the caustic soda sample solution in thesample solution stirring container 8 is calculated on the basis of thesignals from the measurement circuit 18 and the preset counters 16 and17, a digital indicator 20 or a level indicator 21 by which the causticsoda concentration of the caustic soda sample solution is calculatedthrough the use of the said operation circuit 19 is indicated by aradiation means, a printer 22 for printing out said indicated values,and a sequence circuit 23.

24 is a storage tank of a supplementary caustic soda solution, and it isdesigned in such a way that the caustic soda solution in the storagetank 24 is supplied into the cloth treating tank 1 by means of aquantitative pulse pump 25 operating on the basis of the signal fromsaid operation circuit 19 so that the caustic soda concentration of thecaustic soda solution in said cloth treating tank 1 becomes constant, atthe prescribed value. 26, 27 and 28 are electromagnetic valves operatedby the control signal from the sequence circuit 23. Due to the openingand closing movements of these electromagnetic valves, the supply anddischarge of the sample solution into the sample solution stirringcontainer 8 and the circulation of the sample solution in the samplesolution collection container 7 are controlled so as to minimize thetime lag between the caustic soda solution in the cloth treating tank 1and the sample solution in the sample solution stirring container 8.

The construction of an example of the present apparatus is as abovedescribed. The automatic concentration control of an aqueous causticsoda solution in the cloth treating tank by using this apparatus willnow be illustrated in the following.

In the process for soaking a cloth 2 to be treated with a caustic sodasolution 3 in a cloth treating tank 1, the caustic soda concentration ofsaid caustic soda solution is maintained at a constant level by thefollowing procedure. First, a portion of the caustic soda solutionsqueezed out of the cloth that was soaked with the caustic soda solutionthrough the use of a pair of squeeze rollers 5 is introduced by means ofthe pump 6 into the sample solution collection container 7, as a samplethereof while the remainder of said caustic soda solution is returned tothe cloth treating tank 1. Then, said sample solution is introduced bydriving the quantitative pulse pump 9 into the sample solution stirringcontainer 8, and the amount of the sample solution introduced into thesample solution stirring container 8, in this instance, is counted bymeans of the preset counter 16 of the solution control unit 15. Next, bydriving the quantitative pulse pump 12, the sample solution in thesample solution stirring container 8 is diluted with water from thedilution water tank 10 to a prescribed magnification while the resultantsolution is stirred. In this instance, the additional amount of waterfor dilution, i.e., the operated amount from the quantitative pulse pump12, is controlled by means of the signal from the solution control unit15. (The object for dilution of the sample solution is to save theadditional amount of the neutralization agent as will be mentionedhereafter.) Meanwhile, the neutralization agent solution (for instance,sulfuric acid solution) in the neutralization solution tank 11 is addeddrop by drop into the sample solution in the sample solution stirringcontainer 8 by operating the quantitative pulse pump 13. When the samplesolution is neutralized, the electrical conductivity value in theconcentration sensor 14 in the sample solution stirring container 8indicates a minimum value. It is then detected by means of themeasurement circuit 18 that the sample solution reaches theneutralization point, and the additional amount of the neutralizationagent added until the sample solution is neutralized, is detected bymeans of the operation circuit 19. Furthermore, in this instance, fromthe additional amount of the neutralization agent, the caustic sodaconcentration of the sample solution in the sample solution stirringcontainer 8 is detected by means of the operation circuit 19, and thevalue of caustic soda concentration is indicated by means of the digitalindicator 20 or the level indicator 21. Therefore, the caustic sodaconcentration of the sample solution can be ascertained by means of theindicators 20 or 21. It is advisable to provide one or more of saidindicators at positions in the factory which are easily accessible forthe control of said levels of concentration.

When the caustic soda concentration of the sample solution is indicatedin this way, the quantitative pulse pump 25 is operated for supplying adefinite amount of the caustic soda solution in the supplementarycaustic soda solution storage tank 24, calculated by the operationcircuit 19, into the aqueous caustic soda solution 3 in the clothtreating tank 1 so that the caustic soda solution in the cloth treatingtank 1 can be controlled constantly to a prescribed caustic sodaconcentration.

As described in detail in the above, by using the present apparatus, theconcentration of the caustic soda sample solution is indicatedautomatically, and accordingly, the caustic soda concentration of thecaustic soda solution for the immersion of the cloth into the treatingsolution tank can be controlled automatically and constantly to theprescribed value. Therefore, there is no need for an operator for thesolution control as in the conventional manually operated process, andthe concentration control of the caustic soda solution can be doneautomatically at definite intervals. Moreover, according to the presentinvention, the sample solution is neutralized after the solution isdiluted, so that the amount of the neutralization agent can economicallybe saved.

What is claimed is:
 1. An apparatus for the automatic concentrationcontrol of an aqueous caustic soda solution in a cloth treating tankthrough which a cloth to be treated is continuously transported,comprising:(i) a pair of squeeze rollers for squeezing a part of thesoda solution out of a cloth that has been soaked with an aqueouscaustic soda solution in a cloth treating tank; (ii) means forintroducing a portion of said caustic soda solution squeezed out of thecloth taken as a sample thereof in a sample solution stirring containerwhile returning the remainder of said caustic soda solution to the clothtreating tank; (iii) means for adding a neutralization agent to saidcaustic soda solution in said sample solution stirring container; (iv) asensor for detecting the neutralization point of said caustic sodasample solution in said sample solution stirring container while addingthe neutralization agent thereof on the basis of electricalconductivity; (v) means for detecting the original caustic sodaconcentration of said caustic soda sample solution after the addition ofthe neutralization agent on the basis of the amount of theneutrilization agent added until said caustic soda sample solutionbecomes neutralized, as detected by means of said sensor; and (vi) meansfor supplying a supplementary caustic soda solution to the caustic sodasolution in said cloth treating tank for controlling the concentrationof said caustic soda solution to a prescribed value on the basis of thecaustic soda concentration of the caustic soda sample solution detectedby said detection means.